2024:658 - CBC Monkstown, Monkstown Road Upper, Dun Laoghaire, Dublin

A programme of pre-construction test excavations was carried out as part of an Archaeological Impact Assessment (AIA) in advance of a proposed development of sports facilities on the grounds of CBC Monkstown, Monkstown Road Upper, Dún Laoghaire, Co. Dublin. The planning application relates to an area measuring 11.5 acres (c.4.7ha) on the grounds of CBC Monkstown in the townland of Monkstown Farmhouse.

The programme of archaeological testing was undertaken in two phases. Phase 1 comprised nine trenches (T1-T9) and was carried out in March 2024. The discovery of a weir wall in T1 resulted in an addendum request to the National Monuments Service (NMS) for a second phase of testing; Phase 2, which comprised seven additional trenches (T10-T15) and was carried out in May 2024. Phases 1 and 2 comprised a total of sixteen test trenches (T1–T15, and T13A) across the whole site totalling 357 linear metres.

The programme of archaeological testing was undertaken in response to a Planning Condition. The testing works followed on from two previous archaeological studies related to the development scheme; these were a geophysical survey (23R0183) carried out by AMS in August 2023 (Leszczynski & Bonsall 2023), and a desk-based Archaeological Impact Assessment for the scheme submitted in October 2023 (CRDS, Mandal 2023).
The archaeological testing revealed how the originally sloping topography of the area (from south to north) had been built up in the twentieth century to create two level playing fields; there was also evidence of modern disturbance, a modern drainage system, a pit and a spread which appear agricultural in origin, and a weir wall dating to the post-medieval period (as supported by mortar analysis of a mortar sample from the wall). The north–south orientated weir wall appears below the western playing pitch and was picked up over c.66m in six trenches (T1, T10, T11, T13A, T14, and T15). The weir wall descends south to north with the original topography which was raised in the mid-twentieth century to create the level playing pitch. Identified at its highest point at the southern end of the western pitch, at a depth of c.0.35m below ground level (BGL), the weir wall descends to a depth of c.2m BGL at the northern end of the western pitch.

The Archaeological Impact Assessment Report assessed the potential impact on the known archaeology (i.e., the weir wall) that will be caused by the proposed development and investigated and recommended as to how this can be mitigated against. The proposed development will impact upon the subsurface post-medieval weir wall, most critically at the location of a proposed changing room at the south of the site where the weir wall is at its highest (i.e., c.0.35m BGL). In addition, proposed below-pitch drainage in regular parallel trenches at 7m intervals will cut across the top of wall in c.7-8 locations.

The AIA recommended that ground clearance works at the development stage are subjected to a constant monitoring brief by a suitably qualified archaeologist.